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Questions tagged [integer]

For challenges involving the manipulation of integers.

23
votes
18answers
1k views

The Digit Triangles

Challenge: Input: A positive integer \$n\$ Output: Create a list in the range \$[1,n]\$, and join it together to a string (i.e. \$n=13\$ would be the string ...
-4
votes
0answers
69 views

Sort a list of integers using only keyboard shortcuts [on hold]

The challenge Sort a list of integers, result should be the sorted list. The catch is that you can only use keyboard shortcuts of a popular program. Details Sorting is in ascending order. Input is ...
30
votes
23answers
7k views

Could you please stop shuffling the deck and play already?

Challenge: Input: A list of distinct positive integers within the range \$[1, \text{list-size}]\$. Output: An integer: the amount of times the list is riffle-shuffled. For a list, this means the ...
12
votes
9answers
746 views

Source permutation

A permutation of a set \$S = \{s_1, s_2, \dotsc, s_n\}\$ is a bijective function \$\pi: S \to S\$. For example, if \$S = \{1,2,3,4\}\$ then the function \$\pi: x \mapsto 1 + (x + 1 \mod 4)\$ is a ...
6
votes
24answers
524 views

Sum integers in a string

Input A string. Output The sum of all integers in the line. Constraints 1≤Length of line≤500 Sample test Case Input the 5is 108 seCONd4 a Output ...
33
votes
5answers
8k views

Historical difference between `/` and `÷` in mathematical expressions

Introduction: Inspired by a discussion that is already going on for many years regarding the expression \$6÷2(1+2)\$. With the expression \$6÷2(1+2)\$, mathematicians will quickly see that ...
7
votes
7answers
507 views

Check type of an integer

You will receive an integer less than 2000000000 and bigger than -2000000000 and you have to test what type(s) of number this is out of: ...
4
votes
9answers
263 views

Floating over the integers

As you may know, the typical binary floating point numbers in a computer language are quite different than the typical integer numbers in a computer language. Floating point numbers can represent a ...
20
votes
15answers
2k views

Square Root Distance from Integers

Given a decimal number k, find the smallest integer n such that the square root of n is ...
19
votes
25answers
2k views

The Highest Dice

Challenge: Here we have the first 100 items of a sequence: ...
23
votes
3answers
1k views

The Path Of The Wildebeest

Golf a program or function which gives the \$n^{\text{th}}\$ location of the wildebeest who starts at square \$1\$ on an infinite chessboard which is numbered in an anti-clockwise square spiral, where ...
24
votes
15answers
3k views

Matrix Jigsaw Puzzles

Input: An integer n Two equal-sized square matrices (with their width/height being a multiple of n) Output: One of two ...
24
votes
38answers
2k views

Enumerate each series of identical numbers in-place

Given a list of strictly positive integers, go through each distinct number and replace all occurrences of it with successive indices (zero or one based) of a new series. Examples ...
23
votes
18answers
2k views

Collapsing numbers

Let's define the a function on natural numbers \$n\$, written as base 10 digits \$d_k\; d_{k-1}\; \dotsc\; d_1\; d_0\$, as follows: As long as there are equal adjacent digits \$d_i\;d_{i-1}\$, ...
21
votes
12answers
2k views

Eight coins for the fair king

This is a "counterpart" of another puzzle, Eight coins for the fair king on Puzzling.SE. You can read the above puzzle for the background. The details about this puzzle are as follows. A set of 8 ...
21
votes
26answers
2k views

Digital Sumorial

Given an input n, write a program or function that outputs/returns the sum of the digital sums of n for all the bases 1 to ...
25
votes
6answers
1k views

Prime containment numbers (speed edition)

This is sequence A054261 The \$n\$th prime containment number is the lowest number which contains the first \$n\$ prime numbers as substrings. For example, the number \$235\$ is the lowest number ...
21
votes
14answers
2k views

Prime containment numbers (golf edition)

This is sequence A054261. The \$n\$th prime containment number is the lowest number which contains the first \$n\$ prime numbers as substrings. For example, the number \$235\$ is the lowest number ...
23
votes
25answers
2k views

Sort by Largest Digit(s)

Challenge: Given a list of integer, sort descending by their single largest digit(s). The order for numbers with the same largest digit are then sorted by second largest digit, etc. We ignore ...
17
votes
10answers
2k views

Reciprocal copycats

Let \$A\$ be a positive integer consisting of \$n\$ decimal digits \$d_1,d_2,...,d_n\$. Let \$B\$ be another positive integer. For the purpose of this challenge, we call \$A\$ a copycat of \$B\$ if ...
24
votes
15answers
2k views

All the single eights

Given a non-empty rectangular array of integers from 0 to 9, output the amount of cells that are ...
10
votes
9answers
1k views

Through Space and Time

Introduction: In general we usually speak of four dimensions: three space dimensions for x, y, and ...
15
votes
45answers
2k views

Print the Lost numbers

As a big fan of the Lost TV series, I always got intrigued by the sequence of numbers that repetitively appears on the episodes. These numbers are: \$ 4, 8, 15, 16, 23, 42\$ (A104101) Using any ...
14
votes
28answers
2k views

The inverse Collatz Conjecture

I think the Collatz Conjecture is already well-known. But what if we invert the rules? Start with an integer n >= 1. Repeat the following steps: If n is even, multiply it by 3 and add 1. If n is ...
20
votes
22answers
1k views

New Neighbour Sequence

The non-negative integers are bored of always having the same two* neighbours, so they decide to mix things up a little. However, they are also lazy and want to stay as close as possible to their ...
17
votes
19answers
2k views

The Written Digits Sequence

Here's a reasonably trivial sequence which is not in the Online Encyclopedia of Integer Sequences. Start with an empty sequence then define each term as the number of characters required to write out,...
9
votes
24answers
941 views

Multiplicative undelta

Let us define the "multiplicative deltas" of values \$[\; a_0, \cdots a_N, \;]\$ as: $$ [\; a_1 / a_0, \cdots, a_{i+1} / a_i, \cdots, a_N / a_{N-1} \;] $$ The reverse operation - namely "...
13
votes
16answers
834 views

Length of a UTF-8 byte sequence

Determine the length of a UTF-8 byte sequence given its first byte. The following table shows which ranges map to each possible length: ...
15
votes
9answers
609 views

Stagger, stack, sum

Inspired by this Stack Overflow question. The challenge Input An array of square matrices containing non-negative integers. Output A square matrix built from the input matrices as follows. Let \$...
26
votes
18answers
3k views

Make them sum to 10,000

We've recently reached the threshold of 10,000 questions on PPCG. Hooray! Let's celebrate this with a simple challenge. Input Two integers \$A\$ and \$B\$, both in \$[1..9999]\$, such that \$A+B<...
-1
votes
1answer
117 views

Every positive integer can be written as the sum of 3 palindrome integers. Wha'ts the largest possible palindrome integer for each integer n? [duplicate]

Let n be a positive integer then n = a + b + c for some a, b, and c that are palindrome integers. What is the largest possible integer ...
17
votes
18answers
4k views

Longest Repeating Subsequence of a Single Digit

Challenge: Given a positive integer, output the longest single-digit subsequence that occurs at least twice, AND has boundaries of another digit (or the start/end of the integer). An example: Input:...
10
votes
7answers
638 views

Whose neighbours are hostile?

Introduction For the purposes of this challenge, we will define the neighbours of an element \$E\$ in a square matrix \$A\$ (such that \$E=A_{i,j}\$) as all the entries of \$A\$ that are immediately ...
31
votes
41answers
5k views

Half, Half Half, and, Half

Consider the following number sequence: \$ 0, \frac{1}{2}, \frac{1}{4}, \frac{3}{4}, \frac{1}{8}, \frac{3}{8}, \frac{5}{8}, \frac{7}{8}, \frac{1}{16}, \frac{3}{16}, \frac{5}{16}, \frac{7}{16}, \...
16
votes
18answers
5k views

Simplistic Lava Lamp

Introduction: I think everyone knows what a Lava Lamp is, but in case they do not: (Image source) They're basically glass tubes that contain wax in a translucent liquid. The bottom part is heated ...
21
votes
15answers
2k views

Crown hundred crownty crown

I noticed a certain game had a peculiar life counter, which instead of stopping at 999, gained a new digit – the next number was crown hundred or ...
14
votes
15answers
1k views

Missing numbers in arithmetic sum

Challenge Giving a valid arithmetic sum with some missing numbers, output the full expression. Example: ...
6
votes
20answers
421 views

Find the \$\left(n^2\right)^\text{th }n\$-gonal number

Given a non-negative integer, \$n\$, yield the \$(n^2)^\text{th } n\$-gonal number. Further Detail: The \$x\$-gonal numbers, or polygonal numbers, are also known as the two-dimensional figurate ...
12
votes
11answers
1k views

Codegolf Rainbow : Fun with Integer-Arrays

Introduction: (Source: Wikipedia) When we look at a rainbow it will always have the colors from top to bottom: Red; orange; yellow; green; blue; indigo; violet If we look at these individual rings, ...
15
votes
21answers
1k views

Fill up to duplicate ranges

Let \$L\$ be a list of positive integers with no particular ordering, and which can contain duplicates. Write a program or function which outputs a list of positive integers \$M\$ (whose ordering is ...
25
votes
15answers
2k views

Toggle some bits and get a square

Given an integer \$N>3\$, you have to find the minimum number of bits that need to be inverted in \$N\$ to turn it into a square number. You are only allowed to invert bits below the most ...
17
votes
34answers
955 views

Calculate power series result [duplicate]

Related: Calculate Power Series Coefficients Given a positive integer \$X\$ and a max exponent (Also a positive integer too) \$N\$ calculate the result of a power series. Example: $$X^0+X^1+X^2+\...
18
votes
8answers
730 views

Spiral neighbourhoods

If we take the natural numbers and roll them up counter clock-wise into a spiral we end up with the following infinite spiral: ...
13
votes
12answers
2k views

Small Ramsey Numbers

Background: the Ramsey number \$R(r,s)\$ gives the minimum number of vertices \$v\$ in the complete graph \$K_v\$ such that a red/blue edge coloring of \$K_v\$ has at least one red \$K_r\$ or one blue ...
17
votes
7answers
627 views

Stacked digit staircases

Given positive integers \$w\$ and \$h\$ output \$w\$ columns and \$h\$ rows of text as described below. The first row begins with 11 0s, the second row with 10 <...
-1
votes
7answers
405 views

Calculate the sum of all odd digits of pi in range [duplicate]

Introduction In the not so distant future with the AI revolution, we will need a way to solve their captchas to prove we're not humans. This challenge was inspired by CommitStrip. Challenge One ...
7
votes
10answers
535 views

How many bytes is it

This time, we want render the count of bytes in a human readable way to user. Let's write a program (a full one or a function or other acceptable formats) to do this. Input An non-negative integer, ...
25
votes
30answers
2k views

Let's design a digit mosaic

Challenge Given a positive integer \$N\$, repeat each of its digits \$d_1, d_2, d_3, \cdots, d_n\$ a number of times corresponding to its position in \$N\$. In other words, each digit \$d_k\$ should ...
24
votes
29answers
2k views

Replace me by the sum of my cyclic successors!

I have a simple challenge for you this time. Given an array of positive integers A (or the equivalent in your language), replace each entry Ai with the sum of the next Ai elements of A, cycling back ...
16
votes
8answers
591 views

Classify a region by its slope

Definitions The kth ring of a square matrix of size N, where 1 ≤ k ≤ ceiling(N/2) is the list formed by the elements of the kth and (N-k+1)th rows and columns, but without the first and last k-1 ...